Backplanes are used in rack mounted systems to provide interconnections between electronic devices mounted within the rack. Specifically, electronic devices such as processors, interfaces, switches, etc., are supported within a slot of the rack. The said devices are prepared to be inserted into one of the said slots provisioned with connections to the backplane mounted within the rack. Commonly, the electronic device will have a connector, which mates with the corresponding connector of the backplane. The backplane provides interconnection of signals between the devices mounted within the rack and devices external to the rack.
However, prior art backplanes do not provide a good solution for high speed differential signaling above 2.5 Gb/s. The prior art backplane may include ten to thirty layers for interconnections between different slots of the rack system. The problems is that the higher the signaling frequency the higher the losses in signal strength. Specifically, anytime a single interconnect is switched, there is a pulse to the signal trace in the backplane and the material surrounding the trace reacts to this electromagnetic change. The molecules surrounding the trace change orientation due to the pulse in the trace such that heat is generated, thereby causing the amplitude of the signals to decrease. Accordingly, the signals will exhibit a loss in signal strength and be more susceptible to interference.
The prior art backplane is a per se non-exchangeable component of the systems built with them. This specifically prohibits the installation of active or even passive components on the backplanes for high availability systems.
The present invention addresses the above-mentioned deficiencies in the prior art backplane by providing a backplane that minimizes losses in the signals. Specifically, the rear interconnect system of the present invention provides a point to point interconnect method, which supports higher frequency interconnect protocols by reducing the signal loss.
In accordance with the present invention, there is provided a system for transferring signals between at least two electronic modules. The system includes at least one interconnect blade in communication with each of the electronic modules or a subset thereof. The signal or signal pair traces implemented on the interconnect blades may connect to exactly two electronic modules, or they may form a bus connecting to several electronic modules.
Each of the interconnect blades has a substrate and at least two contact areas formed on the substrate. Each contact area connects to a respective one of the electronic modules. Disposed on each of the substrates is at least one conduit operative to transfer the signals. The conduits may comprise wires or optical fibers. Each interconnect blade may include an insulating layer surrounding the conduits. The insulating layer facilitates the transfer of high frequency signals by a conduit comprising a wire.
The substrate of the blade may be a printed circuit board fabricated from a fiberglass material such as FR4. The blade may further include a carrier foil with interconnect traces formed by an etching process on its surface. The insulating area surrounding the wires may be a material such as air, gas or foam, which guarantee a separation distance for the wire from the surrounding substrate such that the high frequency signals flowing through the wires do not waste their energy into heating the substrate. In the case of using wire pairs for differential signaling, the energy loss will decrease significantly, because the symmetrical signaling waves zero out with increasing distance.
The required room for a better suited environment of the signals within the rear interconnect blade is achieved by the invention of said blade being mounted perpendicular to the plane of a conventional backplane. Several interconnect networks, including full mesh interconnects can be partitioned in a way which is compatible to the solution with an array of interconnect blades built according to the invention.